The present invention relates to semiconductor devices, and particularly relates to a technology effective for application to semiconductor devices including a diode element.
A power diode element is used by being connected in anti-parallel to switching elements, which include an insulated gate bipolar transistor (IGBT) and an insulated gate field effect transistor (IGFET) such as MOSFET. It is apprehended that, depending on operation conditions, the power diode element may be broken down if a temporal variation (di/dt) of a current, when a direction of the current turns from a forward direction to a reverse direction at a time of the recovery, becomes extremely large. Therefore, in general, the power diode element is required to have a large value of di/dt for preventing from being broken down, that is, the power diode element is required to have a large destruction immunity during reverse recovery (hereinafter called “reverse-recovery immunity”).
However, in view of predisponency such that a reverse recovery di/dt for the reverse-recovery immunity increases year by year, it is apprehended that the power diode element may be broken down by a current concentration in a peripheral edge portion of an ohmic contact portion in which an anode electrode is contacted to an anode region, and that the break down of the power diode element may be increased by an electric field density in an outer curvature portion that becomes a side surface of the anode region. Accordingly, it is important to enhance the reverse-recovery immunity.
JP 2014-3271A discloses a scheme of providing a p-type annular diffusion region, being contact with a p-type anode diffusion region, on an outside of the anode diffusion region. Because the annular diffusion region is deeper than a p-type anode region, the electric field density in the outer curvature portion, which is the side surface of the annular diffusion region, is relaxed to enhance the reverse-recovery immunity.
It is an object of the present invention to provide a new semiconductor device capable of enhancing the reverse-recovery immunity of the diode element.